Insect pests cause huge economic losses worldwide in crop production, and every year farmers face the threat of yield losses due to insect infestation. Genetic engineering of insect resistance in agricultural crops has been an attractive approach to reduce costs associated with crop-management and chemical control practices. The first generation of insect-resistant crops was introduced into the market in 1996, based on the expression in plants of proteins isolated from the gram-positive soil bacterium Bacillus thuringiensis (Bt). The insecticidal Bt Cry proteins are produced during the sporulation-stage of Bt strains and the proteins accumulate in large cytoplasmic crystals within the bacterium. When taken up by insects, a typical Lepidopteran-toxic Bt Cry protein is solubilized and processed in the insect midgut into an active form of about 60 to 65 kDa. The active protein exerts its toxic effect by binding to the midgut epithelial cells, causing pore formation in the cell membrane, which leads to osmotic lysis of the cells (Gill et al., 1992).
A Bt strain may produce many different toxins. Since the isolation of the first insecticidal crystal protein-encoding gene from Bt in 1981 (Schnepf and Whiteley, 1981), more than 100 Bt Cry toxin-encoding genes have been cloned and insect pests have been effectively controlled by expressing Bt-derived proteins in agricultural important crop species. However, the use of individual Bt proteins is often limited, as most Bt proteins are active against only a relatively small number of the numerous insect pests. Specificity of Bt Cry proteins is thought to be determined by factors such as the activation of the toxin in the insect gut (Haider et al. 1986) and its ability to bind specific receptors (Hofmann et al., 1988).
The risk that susceptible insect species may develop resistance against Bt Cry toxins is widely recognized. Consequently, active efforts have been made to identify novel insecticidal proteins. One strategy that has been used was to screen Bacillus strains for the production of insecticidal proteins during vegetative growth stages, rather than during sporulation stages. Using this approach, a number of “vegetative insecticidal proteins” or “VIPs” have been identified.
Estruch et al. (1996), WO94/21795, WO96/10083, WO98/44137, U.S. Pat. Nos. 5,877,012, 6,107,279, 6,137,033 and 6,291,156 describe the isolation of vip3A(a), vip3A(b) and vip3A(c) from supernatant fluids of Bt strains AB88, AB424 and AB51. According to the authors, these genes encode proteins with insecticidal activity towards a broad range of Lepidopteran insect pests.
WO98/18932 and WO99/57282 describe a number of nucleotide sequences isolated from Bt strains. These sequences are referred to as mis (mis-1 to mis-8), war and sup. According to the authors, the encoded proteins have activity against Lepidopteran or Coleopteran pests.
WO00/09697 describes heat-labile, soluble MIS-type and WAR-type toxins, as well as smaller (1 to 10 kDa) toxins, obtainable from the supernatant of cultures of Bacillus laterosporus strains, which, according to the authors, have activity against Western Corn Rootworm larvae.
WO98/00546 and U.S. Pat. No. 6,274,721 describe the isolation of Bt strains and Bt toxins, which, according to the authors, have activity against Lepidopteran pests.
WO99/33991 describes the isolation of Bt strains and Bt toxins, which, according to the authors, have activity against Lepidopteran pests.
Recently, Selvapandiyan et al. (2001) described the isolation of a gene encoding a protein designated as VIP-S. According to the authors the VIP-S protein showed toxicity against a number of Lepidopteran insect species.
Doss et al. (2002) describe the cloning of VIP3V from strain Bt kurstaki.
WO02/078437 describes VIP3 toxins from Bt, such as VIP3A, VIP3B and VIP3A-B hybrid toxins.
Despite the isolation and characterization of a relatively large number of different insecticidal proteins to date, there remains a need for identification, isolation and characterization of new insecticidal proteins. The reasons for this are manifold. Firstly, due to the specificity of insecticidal proteins towards particular groups of target pests (host insect spectra), there is a need to clone genes encoding proteins with different spectra of activity, so that for different crops and different geographic regions suitable proteins for combating insect pests are available. The specificity of Bt Cry proteins, for example, is mostly limited. Identification of toxins with specificity towards different target insects remains desirable. Second, after prolonged use in one geographic region, insects are known to have the capacity to develop resistance towards chemical insecticides and microbial sprays (for example based on Bt spore-crystal mixtures), and are believed to have the capacity to develop resistance towards plants expressing insecticidal proteins. The development of resistance within insect populations could render existing insecticidal proteins ineffective, creating a need for novel genes and proteins. Third, for health and environmental reasons it is desirable to identify proteins with high, specific insecticidal potency and acute bioactivity towards target insect species.
The present invention provides, including the different embodiments described in the claims, novel nucleic acid sequences and amino acid sequences isolated from Bacillus thuringiensis strains. These nucleic and amino acid sequences are useful to protect plants from insect damage, either by the expression of the nucleic acid sequences within plants under the control of suitable promoters, or by external application of the toxins to the plants. The toxins of the subject invention are distinct from previously-described pesticidal toxins.